1. Division of Epidemiology and Public Health, University of Nottingham, Nottingham, UK
2. Department of Microbiology, Faculty of Life Sciences, University of Benin, P.M.B. 1154, Benin City, Nigeria
3. Heidelberg Institute of Global Health, University of Heidelberg, Heidelberg, Germany and Public Health England, CRCE Chilton, OX11 0RQ, UK
4. Institute of Child Health, University of Benin, P.M.B. 1154, Benin City, Nigeria
5. Nottinghamshire County Council, NG15 7LA, Nottingham, UK